1. Field of the Invention
This invention relates to industrial containers, and more particularly to collapsible, lightweight, free-standing containers designed for transporting bulk material, such as hazardous solid waste, in the form of an aggregate or a slurry.
2. Background Information
Conventional bulk shipping containers generally use either a bag concept or a rigid box concept. The bag type container tends to be lightweight and easily collapsed when empty into a small volume for easy storage and shipping. It is, however, difficult to load and unload because it lacks rigidity and thus will not support itself in an open orientation to facilitate loading. Also it is difficult to handle mechanically, such as with a fork lift, without puncturing the bag. The rigid box design, on the other hand, has the rigidity necessary to facilitate loading, to permit stacking of loaded containers, and to allow easy handling with fork lifts and other mechanical devices. However, by their very nature, such containers are not collapsible and thus require large volume for storing and shipping even when empty.
Recent attempts to overcome these difficulties are described in U.S. Pat. No. 5,323,922 (the '922 patent) issued to J. H. Lapoint, Jr., et al. which is hereby fully incorporated by reference herein. The '922 patent discloses a collapsible shipping container constructed using side wall assemblies made from a double layer of flexible material formed into pockets into which stiffeners are inserted. These containers can be collapsed into a small volume for storage or shipping while empty. They are lightweight and rigid enough that they can be filled and discharged easily, can be stacked during shipment even when loaded, and generally will not slump, tilt, or topple over during shipment. They also have loop type handles so that they can be easily handled by mechanical equipment like fork lifts without danger of breaching the containment integrity of the container.
A drawback of this approach, however, is that it utilizes a relatively complex closure assembly in order to provide the requisite structural integrity to resist spillage of the contents during handling. This closure assembly includes a discrete cover piece, several overlapping layers of flaps on the top of the container, and a relatively large number of flexible ties at spaced locations about the entire periphery of the cover piece. The discrete or non-integral cover piece may become separated from the rest of the container assembly and be lost. Multiple layers of materials tend to increase the cost of manufacturing the container. Moreover, the relatively large number of flexible ties in a complex closure arrangement increases the time and labor costs of using the container in its eventual application. Moreover, the use of ties about the entire periphery of the cover generally requires access to all sides of the container to secure it. This lends to disadvantageously prevent one from placing several empty containers side by side for simultaneous filling, or from otherwise placing a container in confined locations, i.e. against a wall, for filling.
Thus, a need exists for a bulk material container that has a simplified closure assembly, substantially without any discrete or unattached components, and that may be sealed shut from one side thereof to simplify its manufacture and use.